Ammunition for open chamber guns



July 31, 1962 D. DARDlcK 3,045,890

AMMUNITION FOR OPEN CHAMBER GUNS Filed Sept. ll, 1959 2 Sheets-Sheet 1 m F/G.

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INVENToR. 0A W0 MRD/CK July 31, 1962 D. DARDlcK 3,946,890

AMMUNITxoN FOR OPEN CHAMBER GUNS Filed sept` 11, 1959 2 sheets-sheet 2 INVENTOR. DA wo DARo/CK 3,046,890 NITHON FR GPEN CHAMBER GUNS David Dardick, New York, NY., assigner to Dardick Corporation, a corporation of Delaware Filed Sept. 11, 1959, Ser. No. 839,407 12 Claims. (Cl. 11H-38) This invention relates to ammunition for guns and relates more particularly to ammunition for open-chamber guns.

This application is a continuation-in-part of my copending application Serial No. 733,162, filed May 5, 1958, now Patent No. 2,983,233, granted May 9, 1961, and which, in turn, is a division of application Serial No. 454,045, filed September 3, 1954, for Open Chamber Gun and Ammunition Therefor, now Patent No. 2,865,126, granted December 23, 1958.

It is an object of this invention to provide new and improved ammunition for open chamber guns.

It is another object of this invention to provide ammunition for an open chamber gun which will be substantially proof lagainst rupture longitudinally of the case and can be manufactured at a lower cost and with the use of less costly materials than has heretofore been deemed feasible or practical.

Other and further objects and -advantages of this invention will appear from the following description, the accompanying drawings and the appended claims.

In the aforementioned Patent No. 2,865,126, there is disclosed an open chamber gun wherein a rotary ammunition drum of initially cylindrical contour is mounted for rotation on its cylinder axis in a strong and rigid frame. The cylinder surface of the drum is radially depressed over a portion of its area to provide one, and preferably more than one, trough-like recess parallel to the rotational axis of the drum. The recesses are identical in shape, being of uniform non-circular contour from end to end in parallel planes normal to the rotational axis of the drum and tapered in width in said normal planes from a maximum at the mouth of the chamber to a minimum at the base thereof. Each recess constitutes an open cartridge chamber through the open top of which the correspondingly shaped non-circular telescoped cartridge of this invention is adapted to be inserted radially of the drum and to be seated longitudinally of the chamber.

The side walls of each such open chamber converge from top to bottom and may be fiat but are preferably uniformly curved in parallel planes normal to the rotational axis of the drum to the same radius of curvature as the cylinder surface of the drum.

Each chamber runs from one to the other of a pair of parallel planes normal to the rotational axis of the drum and marking, respectively, the barrel end and the primer end of the chamber. The rotary drum is constructed and arranged to provide an escape opening at the barrel end of the chamber through which the bullet or projectile of a cartridge seated within the chamber, may be discharged into the bore of a barrel of the gun in alignment therewith. Likewise, the rotary drum is constructed and arranged to provide an access opening at the primer end of the chamber through which a tiring pin or other suitable firing means may be caused to act on Ithe primer of the cartridge, to lire the same.

In accordance with a preferred construction, each chamber runs from end to end of the drum, the access and escape openings of the chamlber being located in oppo- 3,046,890 Patented July 31, 1962 site end faces of the drum land being of the same size and shape as the chamber in cross section.

The open chambers of the drum are disposed in uniformly spaced relation to each other around 'the circumference of the drum. Thus, for each revolution of the drum, each chamber will travel once around the rotational axis of the drum in a closed circular path. This path, starting from a loading position passes successively through a firing or battery position and an ejecting position, and thence to the loading position again, to complete the cycle. Each chamber, while in transit'through the loading position, is radially supplied automatically with a round of ammunition from a magazine unit which is preferably detachably connected to, and forms a handle of, the gun.

The magazine unit is constructed and arranged to provide an ammunition storage chamber wi-thin its contines, the magazine unit being open at one end and being designed to receive, at the opposite end, a load of ammunition. The ammunition load is arranged in the storage chamber in one or more rows of side-by-side rounds, the rounds being delivered successively through the open end of the magazine unit to successive cartridge chambers of the rotary open chamber drum as it rotates.

The open chamber rotary drum serves as a rotary gating 4and conveying device functioning in rotation to pick-off one round of ammunition at a time from the magazine unit and to convey the round sequentially to the battery position for tiring and thence -to the ejecting position for ejection from the drum. In the latter position, the empty cartridge case is automatically ejected from the chamber by suitable ejecting means projected into the chamber at a suitable phase of the cycle.

The drum is suitably disposed at the open end of the magazine unit to bring the open chambers of the dru-m successively into opposition with a terminal round of ammunition in the opening, as the drum is rotated. To this same end, means are provided at the opposite end of the magazine unit for yieldably urging the row or rows of ammunition in the stationary magazine chamber toward and into contact with the cylinder surface of the rotary drum so that the terminal round of ammunition in a given row will be caused to en-ter and be seated in the first empty open chamber brought into opposition therewith.

The stationary frame of the gun is constructed and arranged to serve as a breech for both the open top and the primer end of each cartridge chamber, when the chamber is in battery position. To this end, the frame is of a conguration to provide longitudinally of the drum axis an arcuate breech surface which is concentric with the drum and is suitably dimensioned in directions normal to and longitudinally of the rotational axis of the drum, to span the open chamber from side-to-side and from end-to-end, when the chamber is in battery position.

The arcuate breech surface has a radius of curvature only slightly larger than that of the drum so that the arcuate surfaces of the drum and breech will be in substantially wiping engagement when in opposing relation to each other. Thus, each open chamber on reaching its battery position will be completely capped by the arcuate breech surface and thus be converted into a closed cartridge chamber of generally triangular shape offering a substantially continuous supporting wall surface against which the cartridge case may expand.

For the purpose of closing the primer end of the open cartridge chamber in battery position, the frame of the gun is also constructed and arranged to provide, normal to the drum axis, a breech surface disposed to lie in opposing closely spaced relation to the primer or butt end of the drum so as to be in substantially wiping engagement therewith. This latter breech surface, like the cylindrical breech surface, is suitably dimensioned to span the recess from side-to-side and from top to bottom thereby to provide a surface against which the primer end of the cartridge may expand and press when fired.

Trigger actuated means are provided for effecting rotation of the rotary drum so as to bring the successive recesses into battery position and for tiring the individual rounds when so positioned.

In accordance with this invention, there is provided a cartridge for use with the open-chamber guns aforesaid wherein the bullet or projectile of the cartridge, together with the propellant therefor, is wholly contained within the case or shell of the cartridge.

Exteriorly, the case is of a contour which is other than circular, and, in its more specific aspects, is of a contour, as to part of its circumference, matching that of the recess of the open-chamber `gun aforesaid in which it is to be seated. As to the remaining part, it is of cylindrical contour matching that of the cylinder surface of the drum. Thus, when positioned in an open-chamber of the gun, the cartridge will t snugly against and be supported by the walls of the chamber. Moreover, because of its cylindrical surface portion it serves to provide, in effect, a continuation of the cylinder surface of the drum over the entire span of the chamber at its mouth. IPreferably, the case is of equilateral triangular shape, each of its sides being arcuate and of equal radius of curvature so that when used in an open chamber whose sides are correspondingly curved, it may be inserted in the chamber with any one of its three yapices :at the bottom of the chamber.

In accordance with a preferred embodiment of this invention, the case, interiorly, is of a contour circumferentially which also is other :than circular so that the gas pressure created within the case on ring will tend to cause the case to assume ra circular shape and thus to be firmly supported externally throughout its entire circumferential periphery by the walls of `the open chamber and by the arcuate breech surface of the gun frame. Advantageously, the internal contour of the case may be geo-metrically similar to its external contour, since the fabrication of the case is facilitated in so doing and the wall thicknesses of the case may be closely controlled within permissible limits. In accordance with the invention, moreover, the thickness of the case is preferably greater at the intersections of the case walls 'than between the intersections. In this way, reinforcement is provided at the corners of the case so that the possibility of the case bursting longitudinally along the line of either joint between the rotary drum yand cylindrical breech surface of the gun, is completely, or substantially completely, eliminated.

The casing is of 1a length coextensive with that of the open chamber in which it is to be used. One of its ends, the primer end, is closed by a primer unit which, in battery position of the open chamber, is adapted on firing of the cartridge to press against and be opposed by the end breech surface of the gun frame.

In accordance with a preferred embodiment of this invention, means are provided within the case for supporting the buillet of the cartridge wholly within the case in annularly spaced relation thereto, and for forming a sealing iiange at the other end, the muzzle end, of the case. The supporting and flangeaforming means as here preferably embodied comprises an imperforated sleeve, preferably of cylindrical contour, disposed centrally and longitudinally of the case in annularly spaced relation thereto, the sleeve being hermetically sealed to the case at its outer end and forming an annular obturating flange thereat. The sleeve telescopically receives, and securely but releasably holds, the bullet in coaxial alignment therewith,

in position to be propelled axially from the case into the bore of the gun barrel. The interior of the case, including the annular space between the sleeve and the case, contains the propellant. Advantageously, the sleeve may be rifled internally, if desired, for co-action with a rotating band on the bullet. In such case, the riing or pre-engraving of the sleeve or bullet should conform in pattern to lthat of the riing of the barrel of the gun with which the cartridge is to be used, it being apparent that the cartridge must be properly indexed in its recess to achieve alignment of the riing of cartridge and barrel. To this end, the cartridge and the open chamber of the gun in which it is to be employed may be of a contour such that the cartridge may be received, or pre-indexed, in the chamber in only one position. It will be understood that since the annular space between the case and sleeve is closed at its outer end by a connecting annular obturating wall portion, the expanding gases in the cartridge on firing will tend -to force the connecting obturating wall into firm sealing engagement with the breech end of the gun barrel, thus effectively preventing escape of the propellant gases during and after passage of the bullet through the escape opening of the recess or open chamber.

In accordance with another embodiment of this invention, the projectile-supporting obturating sleeve, instead of being cylindrical both interiorly and exteriorly and in annularly spaced relation to the case, may be cylindrical with respect to its interior only so as to receive and hold the bullet, and be of a contour and size exteriorly to match the interior contour Iand size of the case `and be received therein in sliding t relation thereto. In such case the sleeve is preferably tapered and reduced in thickness from the inside toward the outside, adjacent its inner end, so as to provide an extended annular surface area against which, on firing, the propellant gases may act to force the sleeve forwardly into gas-sealing engagement with the breech end of the gun barrel.

As case materials copper, brass and aluminum have proved to be highly satisfactory for use at both high and low pressures. In the use of these materials, it is essential, however, that the case with its obturating sleeve have the same non-circular shape in cross-section with respect to its inner surface, that is, interiorly, as it has with respect to its outer surface, that is, exteriorly. With this shape and in the use of a suitable metal or metal alloy such as aforesaid, for the case Wall, the case will be satisfactorily supported throughout its entire circumferential periphery by the chamber walls, without nupturing under the pressure of the expanding propellant gases. 11n lieu of such a metal or metal alloy, a thermoplastic polyolefin resin having an elasticity and fluidity such that the pressure generated by the powder gases will cause the plastic material `to flow momentarily in all directions, may be employed. A preferred polyoilefn resin is a rigid linear polyethylene resin such as that produced catalytically by the low-temperature low pressure process described in U.S. Patent No. 2,825,721 granted March 4, 1958 to Phillips Petroleum Company for Polymers and Production Thereof. By way of example, such resin may be a high density polyethylene resin having a melt index of 0.7 prepared by polymerizing ethylene in a reaction zone at a pressure of 420 pounds per square inch absolute and at a temperature of 280 F in the presence of a catalyst comprising 2.3% by weight of chromium oxide (chromium principally in hexavalent state) on a silica-alumina composite comprising silica and `alumina in a weight ratio of 6.1:1 the catalyst being present in the reaction zone in the form of a 0.05% slurry in cyclohexane and the ethylene and `the ethylene present being in excess of that required to saturate the cyclohexane. The melt index was determined by A.S.T.M. Method D-l 23S-52T and is a measure of the fluidity of the resin. (Melt index, as determined by A.S.T.M. Method D-1238-52T, is the rate of extrusion of a thermoplastic material through an orifice of a specific range land diameter under prescribed conditions of ltemperature :and pressure.)

In accordance with still another embodiment of' this invention, the case is formed of a thermoplastic polyolefln material such as the aforesaid, with the distinction that the interior of the `case is circular in section and the obturating sleeve is eliminated. The exterior of the case still preserves its substantially triangular configuration. With this configuration and in view of the density and elasticity of the material, it appears that the material at the thicker portions of the case Walls, that is, at the relatively thick corners, ows under the pressure of the expanding gases toward the thinner portions intermediate the corners. Thus, the circular interior of the case tends to become noncircular and tends to conform in shape to the non-circular, that is, generally triangular, shape of the exterior. At the same time, the longitudinal expansion of the case made possible by the fluidity and 110W of the plastic material, results in the case being pressed at its forward end into firm sealing contact with the breech end of the barrel. The continued pressure of the expanding gases upon the now non-circular interior of the case tends, just as in the other embodiments of this invention, to expand the case in its entirety into a circular shape in section so as to obtain the desired firm support from the chamber walls over the whole of the side wall area of the case. By reason of the initially circular interior of the case it is poss-ible to extrude the casein one piece.

In the accompanying drawings which form part of the instant specication and in which like numbers refer to like parts throughout the several views,

FIG. l is a view in side elevation with parts in section of an open chamber revolver, the view showing an open chamber of the revolver loaded with the new and improved non-circular, telescoped cartridge of this invention, the open chamber being shown in battery position;

FIG. 2 is a view in section taken along the line 2 2 of FIG. 1 showing an arrangement of cartridges of this invention in parallel rows in the magazine handle of the revolver;

FIG. 3 is a fragmentary view in section taken along the line 3 3 of FIG. 1 showing the rotary chamber revolved from the battery position shown in FIG. 1 to the cartridge ejecting position;

FIG. 4 is a somewhat enlarged fragmentary view in section taken along the line 4 4 of FIG. l, the View showing details ofthe cartridge construction;

FIG. 5 is a fragmentary isometric View of the open chamber revolver of FIG. 1 showing details of the open chamber;

FIG. 6 is a view in section and to an enlarged scale of the ammunition shown in the open-chamber revolver of FIG. 1;

FIG. 7 is a view in section of another embodiment of triangular ammunition in accordance with this invention; the case and obturating sleeve being formed of a plastic material and the propellant being omitted for clarity of showing;

FIGS. 8 and 9 are views in section along the lines 8 8 and 9 9 of FIG. 7;

FIG. 10 is a view in section of still another embodiment of triangular ammunition in accordance with this inventionless the propellant and primer the case being formed of plastic material and being of circular section in its interior;

FIG. 11 is a view in section taken along the line 11-11 of FIG. 10; and

FIG. 12 is a fragmentary view in section of ammunition such as is depicted in FIG. 10 but including the primer and a primer support.

Referring now more particularly to the accompanying drawing, a rotary drum 1 is mounted for rotation on its cylinder axis in a frame 2 by means of coaxially aligned shafts 3 and 4 at its respective opposite ends. The drum is recessed longitudinally to provide a plurality of open 6 chambers 5 which, as here preferably embodied, are three in number and are spaced at equal distances circumferentially around the drum.

The chambers 5 are identical and parallel the rotational axis of the drum. The side walls 6 of each chamber are arcuate in shape, each having a radius of curvature the same as that of the drum. Thus, each chamber is adapted to receive within its contines a cartridge in accordance with this invention having a configuration precisely conforming to that of the chamber. Moreover, each chamber extends from one end to the other of the drum so as to provide an escape opening 7 at one end of the drum and a primer opening S at the opposite end of the drum.

As shown in FIGS. 1 and 2 the drum is in battery position in which the topmost chamber of the three chambers in the drum is aligned with a barrel 9 carried by the frame 2. In this position, the geometrically longitudinal axis 4of the chamber is coaxially aligned with the axis of the bore of the barrel.

The frame 2 forms a breech for the open top of the primer opening 8 of the chamber when the latter is in battery position. To this end, the frame 2 is provided with a cylindrical breech surface 11 which as shown in FIG. 1 spans the chamber from end to end and, as shown in FIG. 2 spans the chamber between the walls 6 and, preferably, is dimensioned lto overlap the walls 6 so as completely to close the open top or mouth of the chamber. The cylindrical breech surface 11 is concentric with the rotational axis of the drum 1 and is of a radius of curvature which is substantially the same as that of the cylinder surface of the drum. Thus, as the drum is rotated, its cylinder surface and the cylindrical breech surface 11 will be in substantially wiping engagement with each other. Moreover, as is best seen in FIG. 4, the cartridge 12 with which the chamber 5 is loaded, is, like the chamber, of non-circular configuration externally matching that of the chamber. The walls '13 o-f the cartridge are, as shown, arcuate in shape and of a radius of curvature the same as that of the drum 1. Thus, when the cartridge is positioned in the chamber, the uppermost wall of the cartridge forms a continuation o-f the cylindrical surface of the drum so that the drum is capable of rotating freely with respect to the cylindrical breech surface 13 of the frame 2. Moreover, since each of the Walls 13 of the cartridge are of the same curvature, the cartridge may be inserted in the chamber 5 with any one of its sides uppermost so that indexing of 4the cartridge with respect to the chamber during the loading operation, is unnecessary.

Closure of the primer end of the chamber 5 in the battery position is effected by a at breech surface 14 which is normal to the rotational axis of the drum 1 and is in closely spaced parallel relation to the breech end surface 15 of the drum. Thus, the breech surface 14 provides a strong and rigid supporting surface against which the primer end of the cartridge 12 is adapted to beai when the cartridge is iired.

The -frame 2 also serves to support a firing pin 16 and a hammer 17 which latter is actuated by suitable trigger mechanism including trigger 18 and hammer-actuating shaft 19.

The shaft 19 is reciprocably mounted in the frame 2, being connected at its one end to the hammer y17 by means of a pin 20l which rides in a slot 21 in the hammer. The opposite end of the shaft 19 is |bifurcated to receive Within the yoke thereby formed, one end of the trigger 18 which latter is provided with an arcuate slot 22 which receives a pin 23 so that rearward movement of the trigger on its trigger pin 24 will effect a forward movement of the hammer-actuating shaft 19 and, in turn, movement of the hammer to a cocked position as shown in FIG. l. The shaft 19 carries a hammer spring 25 concentric therewith tending to drive the head 26 of the hammer against the firing pin 16.

Means are provided for effecting rotation of the drum 1 so as successively .to bring the chambers 5V each to the battery position during cocking of the hammer 17, and to lock the drum in battery position as the hammer falls. As here preferably embodied, the drum shaft or axle 4 which is journalled in the frame 2 is provided at its forward end with a cylinder cam Z7 having a number of camming surfaces 2S disposed longitudinally and circumferentially lthereof, there being one such camming surface for each of the chambers of the drum. A cam actuating lever 29 is pivotally slidably mounted on a pin 3l) carried by the frame 2 so as to engage the camming surfaces 28 one at a time and to rotate the cylinder cam 27 and thus the drum 1 through a 120 angle of rotation for each full rearward movement of the trigger `18. The lever 29 terminates at its one end in a cam actuating surface 31 engaging the cam surface 28 as shown in FIG. 1, and terminates at its opposite end in a slot 32 receiving the pin 23 carried by the trigger 13. The lever 29 is also slotted intermediate its ends as at 33 for the reception of the pivot pin 30 in order that angular movement of the lever on the pin 30 may be accompanied by lengthwise movement of the lever on the pins 30 and 23. Clockwise movement of the lever 29 as viewed in FIG. 1 is opposed by a return spring 34 carried by the frame 2 so that as the cam actuating surface 31 of the lever escapes from the cam surface 28, the lever will be snapped back to its starting position in engagement with the left hand end of lthe next succeeding cam vsurface 28.

Means are provided for locking the drum 1 against rotation in the cocked position of the hammer as shown in FIG. 1. The locking means comprises a detent 35 pivotally mounted on a pin 36 carried by the Yframe 2, the detent being urged into locking position in a recess 37 in the drum 1 by a spring 38 carried by the frame 2. One such recess is provided for each of the chambers in the plane of symmetry of the chamber in the battery position. The detent 35 includes a sear 39 which is pivotally mounted as to 40 on the detent and is adapted to be engaged by an actuating pin 41 of `a pinion 42 which, in turn, operatively engages a rack 43 on the hammer-actuating shaft 19. As will be apparent from FIG. 1, with the parts in the position there shown, the drum 1 is locked against rotation by the detent 35. Further rearward movement of the trigger 1S from the position shown will cause the cam actuating lever 29 to escape from the cam surface 31 thereby releasing the hammer so that it will strike the firing pin 16. In this operation the hammeractuating shaft 19 moves to the right as viewed in FIG. 1 under the action of the spring 25, rotating the pinion 42 in a counterclockwise direction so that the pinion pin 41 engages the sear 39 and displaces it on its pivot pin 40.

The detent will remain in locked position in the recess 37. Then, at the inception of the next rearward movement of the trigger, the pinion pin 41 will engage the sear 39 to rotate the detent 35 in a counterclockwise direction against the action of the spring 38 and thus free the detent from the recess 37. The drum is now free to be rotated by vthe cam 27 driven by the lever 29, this rotation continuing until the next chamber is brought into battery position, at which time, the pinion pin 41 escapes from the sear 39 permitting the spring 38 to move the detent into the related recess 37 in this succeeding battery position.

A magazine unit 46 is detachably connected to the frame 2, the unit forming a handle `for the gun and its interior providing a chamber 47 partitioned centrally between its side Iwalls by a partition member 48 to provide right-hand and left-hand compartments adapted each to contain a vertical row of cartridges in side by side relation. The magazine unit is open at its top and is detachably connected to the frame 2 by a bifurcated clamp 49 at the top of the partition member 48, the clamp having oppositely depressed clamping flanges 50 seated in grooves 51 in the frame 2. By this arrangement the magazine unit can be readily detached for loading With ammunition. As will be seen from FIG. 2, the righthand and left-hand compartments 52 and 53, respectively, of the magazine unit are open at the top so that the topmost round of the row of ammunition in either compartment is adapted to enter the first empty chamber of the drum 1 which comes in opposition to the topmost round. Means are provided for forcing the topmost round into the empty chamber and as here preferably embodied each of the chambers is provided with a spring pressed follower as at 54 and 55 respectively. The follower 54, for example, presses against the bottommost round of the row of ammunition in the chamber 52 thus urging the topmost round into sliding contact with the cylindrical surface of the drum 1. In FIG. 3 the drum 1 is shown in cartridge ejecting position after having been rotated from the battery position shown in FIG. 2. Thus, the right-hand chamber 5 is empty and, when the drum is further rotated the empty chamber will be brought into position with the topmost round in the chamber 52, the round then being forced into and seated in the chamber by the action of the spring pressed follower 54 at the bottom of the chamber. It will be apparent that so long as the empty chamber is loaded with ammunition from the right-hand compartment 52, no ammunition will be transferred from the left-hand chamber 53 into the drum. However, as soon as the right-hand chamber is empty, feeding of the ammunition from the left-hand chamber into the empty drum chamber ywill commence. Moreover, since each cartridge is of generally equilateral triangular coniguration, each cartridge in the row in the respective chambers 52 and 53 can enter the empty chamber in the drum regardless of the arrangement of the cartridges in the magazine unit. It will be apparent that Vthe rotary drum 1 positioned at the open top of the magazine unit serves as a gating and conveying device for preventing the escape of ammunition from the magazine unit and for picking off the topmost round of the row of ammunition for conveyance to the battery position.

Means are provided for ejecting the empty cartridge case from the chamber 5 after tiring. As here preferably embodied, the drum 1 is slotted radially at the bottom of each of the chambers 5 so as to provide thereat a slot 56 within which is pivotally mounted an ejecting lever 57 in such fashion as `to bear upon but not press against the opposing longitudinal apices of the cartridge 12 when the latter is positioned in the chamber. The lever 57 extends beyond the end `15 of 4the drum 1 into a Well 58 in the frame 2, the well 58 `being generally concentric with the drum shaft 3 but having a camming surface 59 (FIG. 3) extending inwardly toward the drum shaft 3. The camming surface 59 is of a configuration suitable to depress the projecting end of vthe ejecting lever 57 as the drum is rotated by the trigger mechanism from the battery position shown in FIG. 2 to the ejecting position shown in FIG. 3, thereby to propel the empty case of the cartridge 12 out of the chamber 5 of the drum as is indicated by the dotted line cartridge shown in FIG. 3. Completion of the .trigger movement brings the empty chamber into the loading position at the open top of the magazine unit, as has been described above.

As has also been described above, the cartridge 12 is of non-circular contour externally and is received in the non-circular chamber 5 of the drum, the chamber being capped or closed in the battery position by the cylindrical breech surface -11. It will therefore be apparent that the cylindrical breech surface 11 and the walls 6 of the open chamber 5 together form a closed chamber for the cartridge 12 in the battery position. The walls of this closed chamber are substantially continuous except for the joints at the opposite sides of the mouth of the chamber 5 where the walls 6 of the chamber abut the cylindrical breech surface 11.

Interiorly, the cartridge 12 is also of non-circular contour so that the expansion of gas within the cartridge on firing will tend to cause the arcuate walls 13 of the cartridge to take a circular contour. In so doing each wall 153 is thereby firmly supported throughout its whole circumferential area by either the walls 6 of the open chamber or the cylind-rical breech surface 11 of the frame 2. 'I'he cartridge walls 13 are reinforced at their intersections with each other so that at the joints of the closed chamber formed by the drum 1 and the frame 2 in battery position, the cartridge case will tbe suiiiciently strengthened to ensure against any possibility of longitudinal bursting of the case at the joints under the pressure of the expanding gases.

Means are provided within the cartridge case formed by the arcuate walls 13 for `supporting a projectile or bullet 60 of cylindrical contour wholly lwithin the interior of the cartridge case and with its axis of revolution in alignment with the axis of the bore '10 of the barrel 9, and for forming an obturating ilange at the muzzle end of the cartridge case adapted to seal hermetically the joint between the cartridge case and the breech end 67 of the gun barrel 9. To this end, a cylindrical sleeve 61 jackets the bullet 6d and terminates at its one end in an annular radially extending flange position 62 whose outer circumferential periphery is of a configuration matching that of the interior of the case formed by the cartridge walls 13. Advantageously, this flange portion 62 .may be formed with a reentrant skirt portion 63 serving to extend the available surface area for joining the flange portion 62. to the walls 13 of the cartridge case.

A primer unit 64 is positioned at and closes the other end of the cartridge case 13, the unit 64 in turn being provided with a primer 65 in coaxial alignment with the longitudinal axis of the bullet V60.

It will be apparent from .the foregoing that the bullet sleeve 61 is in annularly spaced lrelation to the walls 13: of the cartridge so that the pressure of expanding gases within the cartridge will be exerted within this annular space 66 against the annular flange portion 62swhich, in battery position, abuts the breech end 67 of the barrel 9 and thus effectively seals the joint therebetween when the cartridge is fired.

In the embodiment of this invention depicted in FIGS. 7, 8 and 9, the cartridge case 70 and obturating sleeve 71 are each formed, preferably by extrusion, from an olen polymer material such as the aforementioned rigid linear polyethylene. The case 76 is suitably apertured in its end wall 72 to receive a metal primer unit 73 for ig- -niting apropellant (not shown) to be contained in the case between the end wall and the bullet 74.

The case 70 is of equilateral triangular shape-interiorly Vand exteriorly, has arcuate case walls 75 of co-equal radius of curvature, and has the thickened corner p0rtions 76.

The obturating sleeve 71 is of triangular shape Aexteriorly, to match the triangular interior shape of the case and is dimensioned so as to be received snugly slidably in the interior of the case, preferably as a press t. The bore of the sleeve is circular in section to receive and hold the bullet 77 in `a position wholly within the sleeve. Preferably, the sleeveis provided with an annular ange 78 integral therewith which is seated in an annular groove 79 in the bullet, for releasably holding the bullet securely in place in the sleeve pending firing. The wall thickness of the sleeve rearwardly of the locking flange 7S is progressively decreased so as to provide an outwardly tapered surface'Stl against which the propellant gases, on firing, exert pressure to advance the sleeve into firm sealing engagement with the breech end of the gun barrel (not shown). An extended position of the sleeve is shown in dash-dot lines in FIG. 7 but it will be understood that in actual operation it is necessary for the sleeve to advance only a minor amount for it sealingly to engage the barrel end. The thickness of the sleeve is preferably maintained substantially uniform beyond the inner terminus'of lthe inclined surface to form a relatively thin terminal skirt portion 81 against which the expanding gases, on firing, exert pressure radially outwardly to of the case exterior.

l@ assistin increasing the gas seal between the sleeve and case. By employing a press fit between the sleeve and case, entry-of gas'therebetween is minimized and the possibility of` inward collapse of the thin skirt portion 31 is substantially completely avoided.

The leading end of the sleeve 71 is provided with an annular flange 82 whose outer circumferential periphery preferably conforms in shape to the outer circumferential periphery of the case. This flange, on firing, functions as an obturating or sealing flange in contact with the breech end of the gun barrel, to prevent the escape of powder gases through the joint between the barrel and the iiange. It will be understood, however, that the provision of the radially extending sealing flange is not an absolute necessity since the case 70 may be dimentioned to extend to a position flush with the front end of the sleeve and the flange 82 eliminated in its entirety. The flange has the advantage of providing a larger annular sealing area for engagement with the gun barrel and the further advantage that it effectively prevents any accidental movement of the sleeve into the case beyond the point fixed as proper in the assembly of the sleeve and case.

In the embodiment depicted in FIGS. 10 and ll, the cartridge case 85 is formed, preferably, by extrusion, from an oleiin polymer material such as the aforementioned polyethylene. The case 85 has the same substantially triangular exterior shape as is employed for the plastic case of FIG. 7. However, the interior of the case, instead of being of complementary triangular shape, is circular in section and of uniform diameter from endto-end. The end wall 86 of the case is suitably apertured to provide a primer opening 87 for the reception of a primer unit (not shown) such as the primer unit 73 shown in FIG. 7. A bullet 88 of circular section is press-fitted into and wholly within the cylindrical bore 88 of the case and is preferably releasably held securely vtherein by means of an annular flange 89 integral with the case and seated in an annular groove 90 in the bullet S8. It will be understood that the annular flange 89 is, in effect, a snap ring which yields suciently to permit of the bullet being passed therethrough during assembly to a position in which the ring snaps into the groove. In this embodiment the fluidity and elasticity of the plastic material enables the case, on firing, to expand longitudinally sufficiently for the annular sealing surface 91 of the case to sealingly engage the breech end of the gun vbarrel and seal the joint therebetween. The same properties of the plastic material enable ow of the plastic from the thickened corner portions 92 into the thinner wall portions 93 intermediate the corners, so that the resultant internal `deformation appears to be one in which the cylindrical bore of the casing is transformed by the'firing into the generally triangular shape The gas pressure continuing to act on this triangular interior tends to cause the case as such to become circular in cross section and, in so doing, to follow deflection of the chamber walls without loss of support therefrom. Preferably, a circular cupped wad 94 of the same plastic material as the case is positioned immediately aft of the bullet and in close-fitting engagement with the case. The pressure exerted by the firing gases on this wad increases the normal density of the material and results in a radial flow outwardly of the material sufficient to prevent the escape of the gases between the bullet and case during the forward movement of the bullet.

In the embodiment depicted in FIG. 12, the plastic case 95 corresponds to that depicted in FIGS. 10 and 1l, and is provided with an aperture in its 4end wall for the reception of a cylindrical metal cup 96 having an opening 97 in its bottom wall and having an annular lip 98 overlying the end wall 99 of the case 95. The cup 96 is dimensioned to receive and to hold the primer unit 100 securely in position so that on firing the primer flame will pass through the cup opening 97 and the aligned end Wall aperture 101 into the interior of the case. The blow transmitted by the tiring pin to the primer unit 100 could, conceivably, in the absence of the cup, cause the primer unit to compress the plastic material of the end wall sufficiently to permit the primer unit to move inwardly without being detonated. In accordance with this feature of my invention, the stress imposed by the striking of the primer unit is transferred directly to the bottom wall of the cup 96 and thence to the annular lip 98 by which it is distributed over a relatively larger area of the end wall. Inward movement of the primer unit is thus minimized and detonation of the primer assured.

A particularly preferred high density polyethylene resin for use in the plastic ammunition of this invention is the Fortillex A brand of linear polyethylene produced by Celanese Corporation of America in accordance with its so-called A-70 formulation. Typical physical properties of A-70 Fortiflex are set forth in the following table:

TABLE Typical Physzcal and Chemical Properties of F ol'tlflex A ASTM method Units Value Physical properties:

Melt indeX D1238-52'I 0. 6 Density Grams/cc 0.96 Water absorption DMO-54T Percent 0. 01

(24 hr. thick). Brittleness D746-52T F -180 temperature. Heat distortion D648-45T (66 F 194 temperature. p.s.i.).

DMS-45T (264 F 124 p.s.i.). softening F 260 temperature l Suggested highest F 225 use temperature.2 Impact strength 3 D256-47T Ft. lb. per in. 4 to 10 of notch. Compressive D695-52T P.s.l 5, 300

strength (5% offset). Flexural D790-49T P.s.i 6, 600

strength at break. Flemral modulus. D790-49T P.s.i. 10 17 Tensile strength D638-52T .s.i 3, 900

at yield. Tensile strength D638-52T P.s.i 2, 600

at break. Tensile elonga- D638-52T Percent 250 on. Tensile modulus.. D638-52T P.s.i. 10 17 Hardness D676-49T Shore D 60 Mold shrinkage. Length of In. per in .04 to .06

ASTM tensile bar. Width oi In. per in .02 to .04

ASTM tensile bar. Electrical properties: n

Dielectric D149-44 (short Volts/m11 510 strength. time). Dielectric D150-47T constant.

1 kilocyrle 2. 35 1 megacycle 2. 35 Dissipation D150-47T factor.

1 kilocyele 0002 1 megacycle. 0003 Volume resis D257-54T Ohm-cm 6X1015 tivity.

(Cc. cm./cm.2

sec. cm. Hg) (X Gas permeability: 4

Carbon dioxide..- 0. 21 Hydrogen 0. 20 Oxygcn 0. 07 Hclium 0. Ethane 0. 15 Natural nas 0. 07 Freon-l" 0. 06

the molding conditions.

The maximum permissible service temperature will vary with the design of the part, the service conditions, such as the amount of stressing, duration ofthe stress, etc.

3 See table below.

4 As per method outlined by Brubaker & Krammermeyer. Ind. & Eng. Chem. 45:1148 (1953).

CHEMICAL RESISTANCE Change due to 30day immersion at 80 F.

Percent Percent Chemical increase decrease in weight in tensile strength Acetic acid (glacial) 0.73 5 .Acetone 0. 66 l1 Brake iluid 0. l0 3 Carbon tetrachloride 14. 20 15 thanol 0. 14 16 Ethyl acetate- 2. 30 6 Gas ine 6.00 15 Lubricating oil 0. 60 2 Nitric acid (70%) 0. 26 2 N o. 3 nitrogen sol 0.01 5 Oleic acid 0.70 4 Sodium hydroxide (50%) Nil 5 Suluric acid (conc.) 0.01 16 Molding Conditions A /fect Physical Properties As with other plastics, the conditions under which Fortiflex A is molded can substantially modify the physical characteristics of the molded product. Such factors as front and back cylinder temperatures, gate size, molding temperature, interval of cycle, and injection pressures all have a bearing on the end result. To illustrate this relationship, data are presented below on a sample molded under the conditions given.

Condi- Condition I tion II Molding conditions:

Front and back cylinder temperature F.) 310 400 Gate size (mils) 35X105 125)(175 Mold temperature F.) 212 210 Cycle (sec.) 30 60 Injection pressure (lb. gauge) 1,000 500 ASTM method Physical properties:

Tensile:

Break point (p.s.i.) D638-52T 2, 600 2,800 Elongation (percent) 150 280 Modulus (p.s.i. X 100) 10 Flexural: Break point (p.s. 6,500 Impact strength (Izod) (ft.

lb./in. of notch) at- 73" F 10. 4 4. 1 C.) (66 p.s.i.). Hardness (Shore D) DG76-49T 61 61 It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention.

What is claimed is:

l. Ammunition for an open chamber gun comprising an elongated hollow body having, from end to end, an external configuration which, in cross-section, is generally that of an equilateral triangle, said body having relatively thin side walls thickened at the triangle apices and having an end wall at right angles to said side walls, at least one of said side walls having an arcuate outer surface in planes paralleling said end wall; an obturating sleeve telescopically received within said body, said sleeve having an inner end and an outer end, with said inner end being the end nearest said end wall, said sleeve also having, within said body, an external conliguration which, in cross section, iS complementary in size and shape to the internal crosssectional configuration of said body, having a cylindrical bore portion and having a tapered bore portion between said cylindrical bore portion and said inner end of said sleeve, ysaid tapered bore portion tapering radially outwardly in the direction from said cylindrical portion to said inner end of said sleeve; a projectile in said cylindrical bore portion; and, igniter means in said end wall.

2. Ammunition for an open chamber gun in accordance with claim l, said projectile having an annular 13 groove and said sleeve having an annular flange seated in said annular groove.

3. Ammunition for an open chamber gun in accordance with claim l, said sleeve having an annular obturating flange at its outer end, said flange having a circumferential periphery conforming in size and shape to the external conguration of said body.

4. Ammunition for an o-pen chamber gun, comprising an elongated hollow body formed of a high density linear olefin polymer resin having a melt index of not more than approximately .7, said body having, from end to end, an external configuration which, in cross-section, is generally that of an equilateral triangle, having relatively thin side walls thickened at the triangle apices and having `an end wall at right angles to said side Walls, at least one of said `side walls being arcuate in planes paralleling said end wall.

5. Ammunition for an open chamber gun, in accordance with claim 4, in which said resin is a high density linear polyethylene resin.

6. Ammunition for an open chamber gun in accordance with claim 5, in which said high density polyethylene resin has a melt index of approximately 0.7.

7. Ammunition for an open chamber gun, comprising an elongated hollow body formed of a high density linear olefin polymer resin having a melt index of not more than approximately .7, said body having, from end to end, an external configuration which, in cross-section, is generally that of an equilateral triangle and having an internal configuration which, in cross-section, is circular, having relatively thin sidewalls thickened at the triangle apices, and having an end wall at right angles to said side walls, at least one of said side Walls being arcuate in lplanes paralleling said end Wall.

8. Ammunition for an open chamber gun in accordance with claim 7 in which said resin is a high density linear polyethylene resin.

9. Ammunition in accordance with claim 7 in which said side walls each have an arcuate outer surface in 14 planes paralleling said end wall, the respective outer surfaces having the same radius of curvature.

10. Ammunition for an open chamber gun, comprising an elongated hollow body formed of a high density olen polymer resin, said body having, from end to end, an external configuration which, in cross-section, is generally that of an equilateral triangle and having an internal configuration which, in cross-section, is circular, having relatively thin side walls thickened at the triangle `apices, and having an end wall at right angles to said side walls, at least one of said side Walls being arcuate in planes paralleling said end wall; a projectile in the interior of said body; a Wad of high density polyethylene resin between said projectile and said end wall; a propellant between said wad and said end Wall; and igniter means in said end wall.

11. Ammunition for an open chamber gun in accord'- ance With claim l0, including a perforated metal receptacle in said end wall for receiving an igniter means, said receptacle `having an annular rim ange overlying a substantial portion of said end wall.

12. Ammunition for an open chamber gun in accordance with claim 10 in which said projectile is provided with an annular groove and said body is provided inteyriorly with an annular locking ange for engaging said lannular groove.

References Cited in the le of this patent UNITED STATES PATENTS 650,461 Haws May 29, 1900 1,470,591 Behar Oct. 16, 1923 1,659,625 Cowan Feb. 21, 1928 FOREIGN PATENTS 716 Great Britain 1881 560,344 Great Britain Mar. 31, 1944 1,168,999 France Sept. 8, 1958 

